Tonight Missouri is scheduled to kill the convicted murderer Michael Worthington the same way Arizona killed murderer Joseph Rudolph Wood last month: by lethal injection. Wood took two hours to die as he gasped for breath, by one account, "like a fish on shore gulping for air."

Arizona's botched execution by lethal injection marked the U.S.'s fourth this year. One way to put an end to these grotesque and inhumane spectacles, of course, would be to outlaw this method of execution. The only sure way, however, is to abolish capital punishment altogether.

The rationale for death by lethal injection was to provide a more humane way of killing than the gas chamber or the electric chair. It hasn't worked out that way.

U.S. prison officials have been experimenting with new injection formulas because the European companies that make the drugs they once used have stopped selling to them.

Plainly, though, the prison authorities don't know what they're doing. The drug mix that Arizona used on Wood was based on the one that led to a botched execution in Ohio in January. A different combination in Oklahoma in April was supposed to render a murderer unconscious, but instead he writhed and groaned, causing officials to halt the proceedings, whereupon he died of a heart attack. His execution team appears to have had little or no medical training.

States have refused to publicly reveal the qualifications of those teams, the provenance of the drugs they are using or how they developed the new protocols. But they are coming under increasing pressure to do so. The 9th U.S. Circuit Court of Appeals sensibly ruled last month that the public has a right to know this information, although the Supreme Court reversed the decision.

Anticipating that lethal injection will become untenable, some states are considering bringing back the electric chair, the gas chamber or the firing squad. (Although a number of states authorize these methods, none have used them since 2010.) But going backward is no solution. As the Supreme Court has ruled, the Eighth Amendment's prohibition on cruel and unusual punishment draws its meaning from the "evolving standards of decency that mark the progress of a maturing society."

Even if prison authorities were to land upon a new drug protocol that dependably dispatched the condemned without torment or delay, this year's execution record provides other grounds for abolishing the death penalty: To this day, the death penalty is imposed disproportionately on those whose victims were white. Overall, whites make up less than half of homicide victims, yet three-fourths of the victims of men put to death this year were white. And capital punishment is disproportionately meted out to the poor and uneducated.

And then there is a chance that the state will execute an innocent man. In 40 years, more than 130 people have been freed from death row after evidence emerged of their wrongful convictions. Executions make wrongful convictions impossible to correct.

One can debate the rights and wrongs of capital punishment in principle. In practice, this list of disgusting defects is a sufficient case for abolition. A majority of Americans still favor the death penalty, but for the past 20 years opposition has been growing. With prison wardens again drawing curtains around gruesome executions, more Americans may come around to rejecting the idea.

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